Electronics EC /2/2012. * In-class exams: 40% 7 th week exam 25% 12 th week exam 15%

Transcription

1 Arab Academy for Science, Technology and Maritime Transport Electronics EC 331 Dr. Mohamed Hassan Course Assessment * In-class exams: 40% 7 th week exam 25% 12 th week exam 15% *Tutorial exams and activities: 10% (5%with 7 th week exam + 5%with 12 th week exam) * All term activity : 10% (with final) Progress within term (and or) or), Absence in Lecs & Secs (and-or), Bonuses in Lecs only, Dr. evaluation (and-or) and Extra projects-research. Final exam: 40% 1

2 Rules and educational hints (very important) You can view your marks and answer book in all exams any time according to model answer (viewed in Dr or TAs office hours). 25% of any sheet will not be solved intentionally.they will left for your home works OR class activities OR exams in sections OR exams of 7 th and 12 th. You have all wrights to ask about the 25% of previous point in TAs office hours and not in the day of exam and get the true solution but in condition of trying and working before asking. We will construct list contains each student name, Id and for each class. Each student will be responsible for checking his mail 2 times a week during the term for any upgrades related to our subject. Dr is not responsible for error mail- junk- or not giving mails. Dr will send material to each class and contact specific student if any matter happens during the term. Any problem just contact Dr. mhabdazeem@hotmail.com Bonus marks are allowed through good participation in lectures and good outside projects. Students that have lower than 26/50 by end of week 14 will be advised to make (w). (Dr. will send advise through the mail by end of week 14). You have to get the lectures with you each time (printed or on PDAs) to follow up. You have to be prepared for tutorials activities each time (calculatorpapers-pen 2

3 TEXT BOOKS: C.J.Savant, M.S.Rooden, G.L.Carpenter, Electronic Design, Addison Wesley Martin Rodan and Gordon Carpenter, " Electronic Design: from concept to reality REFERENCE BOOKS: Sedra & Smith, Microelectronic Circuits, 5 th edition, Boylestad, Nashelsky, Electronic Devices&circuit theory, Prentice Hall, 2005 Semiconductor Physics: Course Contents Studying semiconductors materials, Extrinsic i materials and semiconductor diodes. P-N junction diode: Theory of operation, Built-in potential, Forward and reverse connections, P-N junction as a circuit element, special diods and P-N junction diode Applications. BJT and MOSFET: Bipolar Junction Transistor (BJT) and Field Effect Transistor (FET) Electronic amplifiers and switches 3

4 Materials Types 1. INSULATORS An INSULATOR is any material that inhibits (stops) the flow of electrons (electricity). An insulator is any material with 5 to 8 free electrons in the outer ring. Because, atoms with 5 to 8 electrons in the outer ring are held (bound) tightly to the atom, they CANNOT be easily moved to another atom nor make room for more electrons. Insulator material includes glass, rubber, and plastic 2. CONDUCTORS Materials Types A CONDUCTOR is any material that easily allows electrons (electricity) to flow. A CONDUCTOR has 1 to 3 free electrons in the outer ring. Because atoms with 1 to 3 electrons in the outer ring are held (bound) loosely to the atom, they can easily move to another atom or make room for more electrons. Conductor material includes copper and gold 4

5 3. SEMICONDUCTORS Materials Types Any material with exactly 4 free electrons in the outer orbit are called SEMICONDUCTORS. A semiconductor is neither a conductor or insulator. Semiconductor material includes carbon, silicon, and germanium. These materials are be used in the manufacturer of diodes, transistors, and integrated circuit chips. Extrinsic Materials: n-type and p-type The characteristic of semiconductor can be altered by adding impurity through doping process (extrinsic material) Two type: 1) N-type 2) P-type 5

6 Extrinsic Materials : n-type N-type is created by introducing impurity elements that have five valence electrons (pentavalent) ex: antimony, arsenic, phosphorus. Note that four covalent bonds are still present, however there is additional fifth electron due to impurity atom. The remaining electron is free to move within the newly formed n-type material. Diffused impurities with five valence electrons are called donor atoms. Antimony impurity in n-type material Extrinsic Materials : p-type P-type is created by doping with impurity atoms having three valence electrons (boron- gallium, indium) Note that there are insufficient number of electrons to complete covalent bonds resulting a hole This hole is ready to accept a free electron The diffused impurities with three valence electrons are called acceptor atoms. Boron impurity in p-type material 6

7 Majority and Minority Carriers In an n-type material - electron is called majority carrier and hole the minority carrier In a p-type material hole is majority carrier and electron is the minority carrier Semiconductor Diode Semiconductor Diode Diode is formed by bringing these two material together p- and n-type. Holes diffuse from the p side to the n side, leaving behind negatively charged immobile negative ions. Electrons diffuse from the n side to the p side, leaving behind positively charged immobile positive ions. Electrons and holes at joined region will combine, resulting in a lack of carriers in the region near the junction (depletion region) 7

8 Reverse-Bias Condition (VD < 0V) Reverse-biased p-n junction Reverse-Bias Condition (VD < 0V) The number of positive ions in the depletion region of n-type will increase due to large number of free electrons drawn to the positive potential. The number of negative ions will increase in p-type resulting widening of depletion region. This region established great barrier for the majority carriers to overcome, resulting I majority =0 A very small amount of reverse current does flow, due to minority i carriers diffusingi from the (p/n) regions into the depletion region and drifting across the junction. 8

9 Forward-Bias Condition (VD > 0V) Forward-biased p-n junction Forward-Bias Condition (VD = 0V) A semiconductor diode is forward-biased when the association p-type and positive voltage and n-type and negative voltage has been established. The application of forward-bias potential will pressure the electrons in n-type and hole in p-type to recombine with ions near the boundary and reduce the width of depletion region The reduction in width of depletion region has resulted in a heavy majority flow across the junction 9